Oral squamous cell carcinoma is the most common malignant tumor of the oral and maxillofacial region. Currently, surgery is the main method of comprehensive treatment. TPF (paclitaxel, cisplatin, and fluorouracil) chemotherapy regimen is one of the important methods for the treatment of oral squamous cell carcinoma. Adjuvant chemotherapy before and after surgery can significantly improve the therapeutic effect of oral cancer patients. Oral mucositis (OM) is a common side effect during chemotherapy, which seriously affects the quality of life of chemotherapy patients and may lead to the termination of chemotherapy. Prevention and treatment of oral mucositis is still an urgent clinical problem. Investigators' previous studies have found that vitamin D can significantly inhibit the proliferation, migration, invasion and metastasis of oral squamous cell carcinoma cells, and vitamin D can protect normal oral mucosal tissue by inhibiting pyroptosis caused by platinum-based chemotherapy drugs. Based on the previous basic research, this project intends to conduct a single-center, prospective, clinical randomized controlled study on the clinical efficacy of vitamin D in reducing oral mucosal inflammation in patients with oral squamous cell carcinoma undergoing TPF chemotherapy, in order to provide evidence-based medical evidence for the clinical use of vitamin D in reducing oral mucosal inflammation in patients with oral cancer chemotherapy. The results of this study are expected to serve as guidelines to guide clinical practice.

Inclusion Criteria:

1. Patients aged 20-70 years
2. Patients with pathologically diagnosed oral squamous cell carcinoma who need TPF-based chemotherapy regimens, and whose expected survival time is greater than 6 months
3. Patients whose serum 25-hydroxyvitamin D level was vitamin D deficiency (<30nmol/L) and adequate (30-50nmol/L) before chemotherapy
4. Patients and their families agree to participate in this trial and sign an informed consent form
5. No cognitive impairment

Exclusion Criteria:

1. People with oral ulcers or other oral mucosal diseases (such as: oral mucosal pemphigus, etc.) at the beginning of the study
2. Patients who are allergic to alfacalcidol drops
3. Patients with severe cardiac insufficiency, liver and kidney insufficiency, and systemic infectious diseases
4. Pregnant women (judged by HCG test) and lactating patients
5. Participating in other clinical trials during the study
6. Those who do not understand or cooperate with clinical trials
7. Patients with hypervitaminosis D, hypercalcemia, hyperphosphatemia and renal rickets